Android 项目必备（四十四）--＞Android 实现悬浮窗

前言

悬浮窗是一种比较常见的需求。例如把视频通话界面缩小成一个悬浮窗，然后用户可以在其他界面上处理事情。

本文将讲解悬浮窗实现步骤、原理、实例代码等

实现原理

1. WindowMananger 接口

Android 的界面绘制，都是通过 WindowMananger 的服务来实现的。那么，既然要实现一个能够在自身应用以外的界面上的悬浮窗，我们就要利用 WindowManager 来实现。

(frameworks/base/core/java/android/view/WindowMananger.java)@SystemService(Context.WINDOW_SERVICE)
public interface WindowManager extends ViewManager {...
}

WindowManager 实现了 ViewManager 接口，可以通过获取 WINDOW_SERVICE 系统服务得到。而ViewManager 接口有 addView 方法，我们就是通过这个方法将悬浮窗控件加入到屏幕中去。

2. LayoutParam 设置

这里需要着重说明的是 LayoutParam 里的 type 变量。这个变量是用来指定窗口类型的。

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
} else {layoutParams.type = WindowManager.LayoutParams.TYPE_PHONE;
}

具体实现

实现一个自动轮播图的悬浮窗。

1. 效果图

2. 声明及申请权限

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

@RequiresApi(api = Build.VERSION_CODES.M)
public class MainActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}@Overrideprotected void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);if (requestCode == 1) {if (!Settings.canDrawOverlays(this)) {Toast.makeText(this, "授权失败", Toast.LENGTH_SHORT).show();} else {Toast.makeText(this, "授权成功", Toast.LENGTH_SHORT).show();startService(new Intent(MainActivity.this, FloatingImageDisplayService.class));}} }public void startFloatingImageDisplayService(View view) {if (FloatingImageDisplayService.isStarted) {return;}if (!Settings.canDrawOverlays(this)) {Toast.makeText(this, "当前无权限，请授权", Toast.LENGTH_SHORT);startActivityForResult(new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + getPackageName())), 1);} else {startService(new Intent(MainActivity.this, FloatingImageDisplayService.class));}}
}

3. 构建悬浮窗需要的控件

image_display.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical" ><ImageViewandroid:id="@+id/image_display_imageview"android:layout_width="wrap_content"android:layout_height="wrap_content" /></LinearLayout>

4. 将控件添加到WindowManager

@RequiresApi(api = Build.VERSION_CODES.M)
public class FloatingImageDisplayService extends Service {public static boolean isStarted = false;private WindowManager windowManager;private WindowManager.LayoutParams layoutParams;private View displayView;private int[] images;private int imageIndex = 0;private Handler changeImageHandler;@Overridepublic void onCreate() {super.onCreate();isStarted = true;windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);layoutParams = new WindowManager.LayoutParams();if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;} else {layoutParams.type = WindowManager.LayoutParams.TYPE_PHONE;}layoutParams.format = PixelFormat.RGBA_8888;layoutParams.gravity = Gravity.LEFT | Gravity.TOP;layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;layoutParams.width = 500;layoutParams.height = 500;layoutParams.x = 300;layoutParams.y = 300;images = new int[] {R.mipmap.image_01,R.mipmap.image_02,R.mipmap.image_03,R.mipmap.image_04,R.mipmap.image_05};changeImageHandler = new Handler(this.getMainLooper(), changeImageCallback);}@Overridepublic IBinder onBind(Intent intent) {return null;}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {showFloatingWindow();return super.onStartCommand(intent, flags, startId);}private void showFloatingWindow() {if (Settings.canDrawOverlays(this)) {LayoutInflater layoutInflater = LayoutInflater.from(this);displayView = layoutInflater.inflate(R.layout.image_display, null);displayView.setOnTouchListener(new FloatingOnTouchListener());ImageView imageView = displayView.findViewById(R.id.image_display_imageview);imageView.setImageResource(images[imageIndex]);windowManager.addView(displayView, layoutParams);changeImageHandler.sendEmptyMessageDelayed(0, 2000);}}private Handler.Callback changeImageCallback = new Handler.Callback() {@Overridepublic boolean handleMessage(Message msg) {if (msg.what == 0) {imageIndex++;if (imageIndex >= 5) {imageIndex = 0;}if (displayView != null) {((ImageView) displayView.findViewById(R.id.image_display_imageview)).setImageResource(images[imageIndex]);}changeImageHandler.sendEmptyMessageDelayed(0, 2000);}return false;}};private class FloatingOnTouchListener implements View.OnTouchListener {private int x;private int y;@Overridepublic boolean onTouch(View view, MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:x = (int) event.getRawX();y = (int) event.getRawY();break;case MotionEvent.ACTION_MOVE:int nowX = (int) event.getRawX();int nowY = (int) event.getRawY();int movedX = nowX - x;int movedY = nowY - y;x = nowX;y = nowY;layoutParams.x = layoutParams.x + movedX;layoutParams.y = layoutParams.y + movedY;windowManager.updateViewLayout(view, layoutParams);break;default:break;}return false;}}
}